Automatic analyzer is a medical testing equipment commonly found in hospitals. Recently, since people have more demand for their own health condition, health examination involving various test items has been growing increasingly. This may therefore raise more demand on the automatic analyzer. For example, in a high-speed automatic biochemical analyzer, a reagent wheel may be highly demanded on its capacity, since more capacity can facilitate and support more test items, and can reduce a frequency of changing the reagent so as to enhance corresponding operation efficiency. The capacity of the reagent wheel may include an amount of a reagent seat arranged thereon and a volume of a reagent container that can be accommodated within each reagent seat. Generally, the larger the capacity of the reagent wheel is, the larger the size of the reagent wheel becomes. Moreover, the reagent wheel with large size may bring about a bigger operation table for the biochemical analyzer. Since operation staff (e.g., a doctor) may sometimes need to perform some operations (such as picking up or placing down the reagent) on the operation table, such table with too large size may result in inconvenient operation. For instance, it may be impossible to reach some reagent seats located in the rear side (the high-speed biochemical analyzer can only be operated from its front side at most of the time, since its rear side is located against the wall and its bilateral sides may be coupled to other module(s)). In addition, the whole equipment may become larger when the operation table is larger in size, which not only causes inconvenience in transportation and placement but also reduces consumer acceptability. Therefore, it is needed to improve the capacity of the reagent wheel while achieving small operation table simultaneously.